The M6 (aka Radeon Mobility) does about 420fps in glxgears. Without DRI it does ~100.
The M7 (aka Radeon 7500 Mobility) apparently works with this code. I can't confirm this as I don't have an ATI Radeon 7500 Mobility to test it on.
The Radeon 9000 Mobility in the 867/1GHz PowerBooks do not work with DRI as far as I know.